Elite Series Stereo Power Amplifiers

Elite Series Mk2 Stereo Power Amplifiers

EL15s Stereo Power Amplifier
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High bias, class AB stereo amplifiers

The Mk2 Elite series amplifiers build upon the original designs with refinements in construction, quality and performance.


The active line receivers have been removed and swapped with an ultra-high performance nickel alloy cored input transformer. This transformer, made specifically for SGR Audio by Jensen Transformers, realizes even lower noise and a true fully-balanced input with complete galvanic isolation.


Power supply upgrades include a smart microprocessor controlled slow charge circuit, which eliminates high inrush currents, and a new symmetrical dual-bridge layout with increased capacitance and lower impedance.

Designed & manufactured in Australia.

Let's face it - the purpose of a power amplifier appears relatively simple. It needs to amplify a low level signal to a voltage which is high enough to drive a loudspeaker while supplying enough current at this higher voltage to drive the loudspeaker's low impedance voice coil. It must do this without clipping or audibly altering the original signal; in other words, the output must be identical to the input, only bigger.


Since the early 1800s, thanks to a German Physicist named Georg Ohm, we've known that power (P) is equal to voltage (V) multiplied by current (I). So given that P = V x I, the job of a power amplifier is to increase both voltage and current, which is actually a fairly trivial task in today's modern world. The difficulty in power amplifier design is achieving low noise and distortion in a compact form factor, and incorporating useful features into the product without degrading the audio quality. At SGR Audio, quality is everything. Quality of design, quality of construction, and quality of service. This results in products with the highest levels of reliability and performance.


The EL Mk2 amplifiers are constructed from a modular design. Across the series, all amplifiers are very similar. As we go up in model, and power rating, all circuits are identical and only the component values change to meet the required current demands. As power output increases, power supply size and output device numbers increase. To fit the larger/extra components required, the chassis size increases. Simple as that really.


Under the hood, the stereo and mono amps look almost identical, sharing exactly the same PCBs but with the mono amps being a bridged version of the stereo. Where most bridged amplifiers use the combination of an inverting and a non-inverting amplifier stage, both halves of the EL series monoblocks are non-inverting and 100% identical. The required phase splitting to drive the bridged configuration is performed by ultra-high-performance, custom-made Jensen Transformers, which provide a perfectly balanced input while remaining compatible with singled ended connections. The EL stereo amps require one Jensen transformer per channel whereas the mono amps require two for optimal isolation and circuit symmetry.


Many years ago, line level transformer performance was simply nothing to get excited about. Fortunately, with today's technology and available materials, companies like Jensen Transformers have pushed the boundaries to create devices which are close to perfect. Unfortunately, performance at this level comes at a price due to the Nickel alloy cores required, meaning that they are too expensive for use in all but the finest high-end audio components.


The popular benefits of input transformers are widely mentioned elsewhere, but with their implementation in the Mk2 EL series, a less-commonplace benefit was the ability to remove all active low level signal circuitry, including the associated power regulators. We no longer needed them; in fact, the overall component count was reduced by 15%, resulting in lower noise and increased transparency.


At the center of each amp is a microprocessor which controls all of the functions of the amplifier. It monitors all power supply rails, temperature sensors, and signal levels as well as responding to the user-selectable option switches on the back panel. Operating at 40 MHz, it can instantaneously detect system failures or output clipping and shut down the output stages to avoid damage to the connected loudspeaker/s. Included in the Mk2 is a new soft-start circuit, where the microprocessor slowly charges up and monitors the power supply, rather than the common instant connect method which requires over-rated fuses to combat the high in-rush current when the power is plugged in. Ever see your lights dim when you plugged in your old power amp?


When you consider that 50% of the EL chassis is the much needed heatsink, combining the rather bulky power supply and delicate amplifier stages into the small central form factor was no mean feat. To minimise interference produced by the toroidal transformer, not only is it shielded and custom wound in a low-noise construction, but the entire power supply is effectively enclosed in its own section and separated from the amplifier PCB by a 4 mm thick solid plate of highly permeable plated steel. This is often referred to as "clean box, dirty box" design, although the EL series amps realise this in the one chassis, avoiding the need for annoying umbilical cords. To bring the power rails up to the amplifier circuits, we've stuck with our design philosophy against wire looms and used custom machined solid copper buss bars that are gold plated for maximum conductivity.


We believe that the overall purity and incredible clarity of musical micro-detail stems largely from the EL Series PCB layout, where we have spent a lot of time and effort optimising. We discovered a long time ago that even identical circuits (and components), with different PCB layouts can sound quite different. The reason for this is internally generated interference. Large currents flowing in PCB traces can emit strong magnetic fields which can couple into other sensitive areas of the circuit. To combat this scenario, our 4 layer circuit boards allow a Field Cancellation Topology (FCT), which cancels out these damaging magnetic fields. Due to the higher current demands at low frequencies, this effect is most often noticed musically as "tight and detailed bass", something which SGR Audio has become well known for.

Input Stage
  • Fully Balanced, high performance, universal input for single ended or balanced connections.
  • Neutrik A series "state of the art" XLR connector.
  • Jensen custom designed ultra-high performance nickel alloy cored input transformer.
  • True galvanic isolation - no possibility of ground loops.
  • Ultra low noise and distortion.
  • Deviation from linear phase (DLP) of less than 1 degree across the audible band.
  • Extremely high CMRR over a wide range of source impedance imbalances.
Output Stage
  • ThermalTrak output devices eliminate thermal lag time and bias trimming.
  • Instant thermal bias with near-perfect thermal stability.
  • Minimal warm-up time.
  • High bias, class AB operation, with the frist few critical watts in pure class A.
  • Gold plated, pure copper output buss bars.
  • Dual, mirrored binding post arrangement allows neater connection for un-symmetrical speaker cable pairs.
  • WBT's nextgen "flagship" binding posts, silver conductors, fully insulated with platinum outer metal cap.
  • Binding posts accept bananas and spades, as well as crimped cable ends up to 11AWG.
Microprocessor Controlled
  • Auto signal detection*. Software algorithm driven, no false triggers!
  • Auto power down*. Software algorithm driven, no false cut-outs!
  • Output power usage and clipping indicator*
  • Clip detection with instant self protect*
  • Real time power supply and temperature monitoring with thermal limit cutout.
  • "Stealth" mode for invisible operation* - no more annoying LEDs!
  • Loss of power detection with instant output muting.

* Back panel switch selectable feature

Printed Circuit Board
  • 4 Layer PCB construction with twice the industry standard copper thickness.
  • 100% symmetrical channel layout.
  • Optimised star grounding avoids output, supply and bypass return currents from flowing in sensitive signal paths.
  • Field Cancellation Typology (FCT) dramatically reduces power rail and output stage radiation resulting in lower noise and interference.
  • Highly thought-out layout and 100% PCB connectivity avoids wire looms and messy "rats nest" construction.
  • Ultra-sonic cleaning to remove all solder flux residue and impurities.
Power Supply
  • Custom low noise and low radiation toroidal transformer includes electrostatic screen and magnetic shield.
  • Isolated power supply chassis section further reduces 'hum and buzz' interference.
  • Symmetrical power supply design with dual high current 35A bridge rectifiers.
  • Panasonic and WIMA capacitors throughout.
  • Gold plated solid copper buss bars.
  • Microprocessor controlled soft-start circuit eliminates high in-rush current, removing the need to over-spec fuse ratings.
  • Field Cancellation Typology (FCT) dramatically reduces radiated noise from high current traces.
Chassis Design
  • All panels are precision CNC machined from aerospace aluminum alloy.
  • Low susceptibility to electromagnetic interference.
  • Internal "clean box / dirty box" separation by 4mm thick high permeability solid plate.
  • Large, solid heatsinks for highly efficient cooling.
Circuitry & Operation
  • WIMA polypropylene and Panasonic electrolytic capacitors.
  • VISHAY Bulk Metal Z-Foil audio resistors ensure high resolution and ultra-low noise floor.
  • MILLS high power audio resistors, completely non-magnetic and non-inductive.
  • Input switching by fully sealed high reliability telecom grade relays (separate relay per channel).
  • No turn on/off "thump".
  • "Click and pop" free transition from standby to play mode.
  • Soft-start circuit with low in-rush current.
  • Output muting without relays in the signal path.
Warranty
  • 5 year return to base warranty
SGR Audio EL15s Stereo Power Amplifier SGR Audio EL30s Stereo Power Amplifier
  • EL15S
  • EL30S
General Specifications
Channels: 1
Gain: 28dB
Input Impedance: 40K
Bandwidth: 0.5Hz - 80Khz, -3dB points
Amplifier Class: Class AB
Mains Voltage: 240VAC / 50Hz, 230VAC / 50Hz, 220VAC / 50Hz, 120VAC / 60Hz, all options +/- 10%, not user selectable.
Model Specific
EL15S EL30S
Power output 8 ohms:
per channel, RMS at onset of clipping, both channels driven
75W 150W
Power output 4 ohms:
per channel, RMS at onset of clipping, both channels driven
100W 225W
Power output 2 ohms:
per channel, RMS at onset of clipping, both channels driven
150W 250W
Output Devices:
per channel
6 6
Minimum load: 2 ohms 2 ohms
Damping Factor: TBA TBA
Distortion: THD+N TBA% THD+N TBA%
S/N Ratio: TBAdB TBAdB
Power Consumption: TBA, TBA standby. TBA, TBA standby.
Product Weight: TBAkg TBAkg
Product Dimensions: 430mm (W)
240mm (D)
88mm (H)
430mm (W)
240mm (D)
132mm (H)
Shipping Weight: TBAkg TBAkg
Shipping Dimensions: TBAmm (W)
TBAmm (D)
TBAmm (H)
TBAmm (W)
TBAmm (D)
TBAmm (H)
Colour Options
  • Black
  • Silver